PLN20170059 Request for Additional Information.pdfCITY OF EDMONDS
121 5ch Avenue North, Edmonds WA 98020
Phone: 425.771.0220 • Fax: 425.771.0221 • Web: www.edmondswa
DEVELOPMENT SERVICES DEPARTMENT • PLANNING DIVISION
f'oC. 18y"
January 31, 2018
Mr. Terrance Wilson
Via email: twilson@wilsonlawgro]ap.com
SUBJECT: REQUEST FOR ADDITIONAL INFORMATION FOR SHORT PLAT
APPLICATION LOCATED AT 18227 80TH AVE. W, FILE NO. PLN20170059
Dear Mr. Wilson:
Your land use application for a two -lot short plat located at 18227 80t1i Ave. W became procedurally
complete pursuant to Edmonds Community Development Code (ECDC) Section 20.02.002 on December
29, 2017. During staff s continued review of your application, however, it was determined that additional
information/clarification is necessary. Please provide responses to the following items at your earliest
convenience so that staff s review of the proposal can continue:
1. Refer to the enclosed memorandums from JoAnne Zulauf, Engineering Technician, and Zack
Richardson, Stormwater Engineer, both dated December 29, 2017. As part of your response,
please include a cover letter stating how each comment was addressed. Any questions on the
comments in the enclosed memorandums may be directed to JoAnne Zulauf at
JoAnne.Zulauf@edmondswa.gov or (425) 771-0220.
2. Refer to the enclosed memorandum from Kevin Zweber, Fire Marshal, dated December 5, 2017.
Please address these comments in your response. Any questions on the enclosed memorandum
may be directed to Kevin Zweber at Kevin.Zwebergedmondswa.gov or (425) 771-0213.
Please submit the above information to the Planning Division as soon as possible so that staff may
continue processing your application. Please keep in mind that a complete response to this information
request must be received within 90 days or the application will lapse for lack of information (ECDC
20.02.003.D). Thus, your application will expire if the requested information is not received by May],
2018. If you have any questions, feel free to contact meat Jen.Machugagedmondswa.gov or (425) 771-
0220.
Sincerely,
Development Services Department - Planning Division
Jen Mach uga
Associate Planner
Cc: File No. PLN20170059
Phong Le (via email: clearvisionhomekgmail.com)
Enclosure: Memorandum dated December 5, 2017 from Kevin Zweber
Memorandum dated December 29, 2017 from JoAnne Zulauf
Memorandum dated December 29, 2017 from Zack Richardson
t ED
-"+ CITY OF EDMONDS
f DEPARTMENT OF FIRE PREVENTION
RE MEMORANDUM
ARTS
December 5, 2017
To: Jen Machuga, Associate Planner
From: Kevin Zweber, Fire Marshal
Re: Plan Check: PLN20170059
Address: 18227 80th Ave W, Edmonds
Project: 2 Lot Plat
After review of the preliminary plans for the above project, it was found that the
following will be required-
1. A new fire hydrant is required, located at the corner of 80th Ave W and the
new access driveway. IFC 507 and ECDC.
2. If driveway grade is greater than 12% residential fire sprinklers will be
required in the new structures.
3. If the driveway access is combined, a fire access road may be required.
Kevin Zweber
Assistant Chief — Fire Prevention Services
Fire Marshal
City of Edmonds,
Department of Fire Prevention
IMI
Date:
To:
From:
Subject:
MEMORANDUM
December 29, 2017
Jen Machuga, Associate Planner
JoAnne Zulauf, Engineering Technician
PLN20170059, Clear Vision 2-lot short plat
18227 801h Ave W
The comments provided below are based upon review of the preliminary civil plans &
documents for the subject short plat. Additional information is requested from the applicant
at this time in order to continue review of the application and provide preliminary approval of
the short plat. Please ask the applicant to provide a written response to each of the
outstanding comments below and revise and resubmit plans accordingly.
1) Verify rim elevation of public sewer manhole. Our records state the invert is 22" (1.83 ft)
for manhole 5-11, not 5 ft as indicated on the plans. If the rim of the manhole is at an
elevation of 315, the invert would be 313.17. Please review the elevations and make the
appropriate changes to the sewer system.
2) Please review Edmond's standard detail for 2 lot short plats, E2.6 (available on the city's
website). Please note the minimum widths necessary for the access road, driveways and
turnarounds. The Fire Marshal may require increased road width and turnarounds
depending which will override the E2.6 standards. Please check with the fire marshal
before revising plans.
3) Pervious paving system shall be required to withstand the following Fire Truck Wheel
and Axle Loads:
Total load on the front axle: 23,000 lbs
Gross vehicle weight: 75,000 lbs
Total Load on Rear Axles: 48,000 lbs
Please provide manufacturers maximum load capacity.
4) Note: Contact PUD as soon as possible to start the approval process for the relocation of
the power pole. Approval in writing from PUD indicating exact proposed location will be
required during civil review of the frontage improvements.
Please also see the stormwater engineer's comments attached.
City of Edmonds
Thank you.
STO RM WATE R REVIEW COMMENTS
City of Edmonds
Engineering Division
To: Engineering Reviewer
Date: December 29, 2017
Project Name: Clear Vision (2-lot Short Plat)
Permit Number: PLN20170059
Address: 18227 80t" Ave W
Review Type: Preliminary P' ' 'r 3sibility)
Submittal Date: 12/1/17
Reviewer: Zack Richardson, PE
City of Edmonds, Stormwater Engineer
Recommendation: I recommend that approval of PLN20170059 be withheld until the
comments below are adequately addressed.
Review Comments:
1. General: It does not appear that any form a preliminary drainage report was
submitted; submit a stormwater site plan report in compliance with SWMMWW
Chapter 1-3.
a. Report shall include downstream analysis and preliminary sizing of all
propose BMPs and/or drainage facilities.
2. General: In either the drainage report or geotechnical report, an engineer shall
evaluate and analyze impacts of a proposed fill rockery/wall immediately
adjacent to a proposed infiltration facility (pervious pavements) and propose
mitigation measures (impervious liner, etc) as needed to ensure infiltration is
achieved (vs cycling flow into wall drainage system or through wall).
3. Soils Report: It is not clear that infiltration rate has been properly determined;
modify soils report as needed to ensure procedures and corrections factors are
compliant with Edmonds Addendum Appendix B and Checklist #4 (attached).
Specifically address:
a. Clarify if soaking period was conducted and provide description of soaking
period as needed.
b. Note the dimensions of the test pit and method of erosion/splash control
utilized while filling pit.
Page 1 of 2
c. Clarify if post-test excavation was conducted and provide
description/analysis as needed (see "Groundwater Mounding" section of
Checklist #4).
d. Re -calculate the correction factor using values within the ranges permitted
in Checklist #4
e. Expand on the potential impacts of the encountered groundwater on the
ability of the site to infiltrate (ie. does a `seasonal ground water condition'
mean the infiltration will be ineffective during wet -season?).
Additional Direction:
The following comments are not required to be addressed in order to demonstrate feasibility for
preliminary plat approval, but will need to be addressed prior to civil construction approval. These
comments are provided for reference to aid the engineer in revising the plans for the next phase and
allow for preliminary adjustments where desired.
• Pervious pavements over 3% require check -damns and will need to be added;
consult Checklist #11 prior to final design.
• Ensure drywell is sited to comply with setback requirements for the future product
type anticipated; currently shown overlapping a portion of the future home.
• Show wall and home footing drain outlet locations; if out letting to the infiltration
facility, ensure enough elevation information is provided to avoid backwatering
the footing drains.
• Ensure the downslope away form the interceptor trench has enough support or
berm width to adequately retain the trench and collection of water within the
trench.
• Provide top and bottom elevations for each infiltration facility and provide a
dimension for where the perforated pipe sits vertically in each system. (Current
drywell rim appears low.)
• Ensure TESC plan adequately protects the pervious pavement infiltration area.
Page 2 of 2
¢n
,a9City of Edmonds
Public Works Department, Engineering Division
121 5th Ave N
Edmonds, WA 98020
Checklist 4:
Methods for Determining Infiltration Rates
Per ECDC 18.30, all Category I projects must comply with Minimum Requirements No. 1 through No. 5,
and all Category 2 projects must comply with Minimum Requirements No. I through No. 9. If infiltration
facilities are proposed to meet Minimum Requirement Nos. 5, 6, and/or 7, soil infiltration rates must be
measured using approved soil infiltration testing procedures.
Infiltration facilities shall be prepared in accordance with the Department of Ecology's Stormwater
Management Manual for Western Washington (SWMMWW), ECDC 18.30, and the requirements in the
Edmonds Stormwater Addendum (Addendum). Because the SWMMWW does not always include clear
itemization of project procedural and/or submittal requirements, the City of Edmonds developed
Appendix B of this Addendum (Methods for Determining Design Infiltration Rates) as well as this
accompanying checklist to aid project proponents and plan reviewers in complying with the applicable
SWMMWW requirements. In addition City -specific requirements (i.e., requirements presented in
ECDC 18.30 and the Addendum that are not included in the SWMMWW) are also included in the
appendix and checklist.
This checklist reflects most, but not necessarily all, of the items that shall be performed by the project
proponent, and documented for review by the Engineering Division. It is intended to be used as an aid for
developers and plan reviewers by providing a foundation for clear and consistent infiltration evaluation
processes in the City of Edmonds. However, all items may not be applicable to every project, and all
items of concern to this office may not be covered on this checklist. Project proponents must review
Appendix B in detail to identify complete infiltration testing requirements. Last, methods and procedures
outlined herein can vary depending on the project. The headings outlined below represent the City's
recommended process, though variations are acceptable as long as all of the required information is
evaluated and documented.
Applicant:
Application #:
ADDENDUM CHECKLIST 1
Within each blank cell, enter comment codes as follows:
C = Complete R = Revise (i.e., make corrections)
N/A = Not Applicable M = Missing (i.e., please include)
IC = Incomplete
APPLICATIONS
(SWMMWW Volume III, Section 3.3.5)
Method 1— Field Testing
Large -Scale Pilot Infiltration Test (PIT) applies to infiltration facilities with drainage areas
greater than I acre (i.e., projects that are using the "Detailed Method"- see Addendum
Checklist 6), and may be used to demonstrate infeasibility of bioretention, permeable
pavement, or rain gardens in meeting Minimum Requirement No. 5.
Small -Scale Pilot Infiltration Test (PIT) applies to infiltration facilities with drainage areas
less than 1 acre (i.e., projects that are using the "Simple Method"- see Addendum
Checklist 6), and may be used to demonstrate infeasibility of bioretention, permeable
pavement, or rain gardens in meeting Minimum Requirement No. 5.
U.S. EPA Falling Head Percolation Test Procedure (as Modified for the City of Edmonds)
may only be used for BMP performance verification testing. May not be used for BMP
design or to demonstrate infeasibility of bioretention, permeable pavement, or rain gardens
in meeting Minimum Requirement No. 5.
Method 2 — Soil Grain Size Analysis
Soil Grain Size Analysis may only be used at project sites that are underlain by soils not
consolidated by glacial advance (e.g., recessional outwash soils), and may not be used to
demonstrate infeasibility of bioretention, permeable pavement, or rain gardens in meeting
Minimum Requirement No. 5.
PROCEDURES
(SWMMWW Volume 111, Section 3.3.5 and 3.4)
See Addendum Appendix B — Methods for Determining Design Infiltration Rates, as well
as Addendum Checklists 5 and 6.
Correction Factor
(SWMMWW Volume 111, Section 3.3.6)
For application of correction factors for bioretention, permeable pavement, and rain
gardens, refer to SWMMWW Volume III, Section 3.4; Addendum Appendix B; and
Addendum Checklist 5: Field and Design Procedures for Bioretention, Permeable
Pavement, Rain Gardens, and Downspout Infiltration Systems for application of correction
factors.
►_1DID] 40pill L[y.IXy34&1EI
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Within each blank cell, enter comment codes as follows:
C = Complete R = Revise (i.e., make corrections)
N/A = Not Applicable M = Missing (i.e., please include)
IC = Incomplete
For all other infiltration facilities, the design saturated hydraulic conductivity is calculated
using the following equation:
Ksatdesig. = Ksatinitiai x CFv x CFT x CFM
CFv = CF for site variability and number of test locations
• 0.33 to 1.0
• High uncertainty in subsurface conditions = lower CFv
• High certainty in subsurface conditions = higher CFv
CFT = CF for test method used
• For the large-scale PIT method, CFT = 0.75;
• For the small-scale PIT method, CFT = 0.50
• For other small-scale infiltration tests (e.g., EPA falling head), CFT = 0.40
• For grain size analysis, CFT = 0.40.
CFM = CF for influent control to prevent siltation and bio-build up = 0.9.
Method 1— Field Testing
(SWMMWW Volume III, Section 3.3.6)
Large -Scale Pilot Infiltration Test (PIT)
Preparation of Test Hole
Excavate the test pit to the depth of the bottom of the proposed infiltration facility.
Lay back the slopes sufficiently to avoid caving and erosion during the test, or consider
shoring the sides of the test pit.
The horizontal surface area of the bottom of the test pit should be approximately 100 square
feet.
Accurately document the size, location, and geometry of the test pit.
Install a vertical measuring rod (minimum 5 feet long) marked in 0.5-inch increments in the
center of the pit bottom.
Convey water to the pit using a rigid 6-inch diameter pipe with a splash plate on the bottom
to convey water to the pit.
Soaking Period
Pre-soak: Add water to the pit at a rate that will maintain a water level between 6 inches and
12 inches above the bottom of the pit.
Note: For infiltration facilities serving large drainage areas, designs with multiple feet of
standing water can have infiltration tests with greater than 1 foot of standing water. The
depth must not exceed the proposed maximum depth of water expected in the completed
facility.
Every 15 to 30 minutes, record the cumulative volume and instantaneous flow rate (in
gallons per minute) necessary to maintain the water level at the same point on the
measuring rod.
ADDENDUM CHECKLIST
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2,
30
Within each blank cell, enter comment codes as follows:
C = Complete R = Revise (i.e., make corrections)
N/A = Not Applicable M = Missing (i.e., please include)
IC = Incomplete
Add water to the pit until 1 hour after the flow rate into the pit has stabilized while
maintaining the same pond water level (usually 6 hours). The total of the pre-soak time plus
1 hour after the flow rate has stabilized should be no less than 6 hours.
Measurement of the Infiltration Rate
After the flow rate has stabilized for at least 1 hour, turn off the water and record the rate of
infiltration (the drop rate of the standing water) in inches per hour from the measuring rod
data, until the pit is empty. Use 30-minute or 1-hour increments.
Calculate the Design Infiltration Rate
Calculate and record the infiltration rate in inches per hour. Use the lowest hourly rate
determined in row 17 above.
To compute the design infiltration rate (Ksatd,sign), adjust the final measured infiltration
rates by the appropriate correction factors outlined above.
Groundwater Mounding
Over -excavate the pit to see if the test water is mounded on shallow restrictive layers or if it
has continued to flow deep into the subsurface. The depth of excavation varies depending
on soil type and depth to hydraulic restricting layer, and is determined by the design
professional engineer or certified soils professional. Mounding is an indication that a
mounding analysis is necessary.
Small -Scale Pilot Infiltration Test
Preparation of Test Hole
Excavate the test pit to the estimated surface elevation of the proposed infiltration facility.
For bioretention, excavate to the estimated elevation at which the imported soil mix will lie
on top of the underlying native soil.
For permeable pavements, excavate to the elevation at which the imported subgrade
materials, or the pavement itself, will contact the underlying native soil.
Lay back the slopes sufficiently to avoid caving and erosion during the test, or consider
shoring the sides of the test pit.
The horizontal surface area of the bottom of the test pit should be 12 to 32 square feet.
Accurately document the size, location, and geometry of the test pit.
Install a vertical measuring rod that is marked in 0.5-inch increments in the center of the pit
bottom.
Convey water to the pit using a rigid pipe with a splash plate on the bottom to convey water
to the pit. Use a 3-inch-diameter pipe for pits on the smaller end of the recommended
surface area, and a 4-inch pipe for pits on the larger end of the recommended surface area.
Soaking Period
Pre-soak: Add water to the pit so that there is standing water for at least 6 hours. Maintain
the water level at least 12 inches above the bottom of the pit.
Add water to the pit at a rate that will maintain a fixed 6- to 12-inch water level above the
bottom of the pit over a full hour. The depth should not exceed the proposed maximum
depth of water expected in the completed facility.
ADDENDUM CHECKLIST
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10
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39
40
43
Within each blank cell, enter comment codes as follows:
C = Complete R = Revise (i.e., make corrections)
N/A = Not Applicable M = Missing (i.e., please include)
IC = Incomplete
Every 15 minutes, record the cumulative volume and instantaneous flow rate in gallons per
minute necessary to maintain the water level at the same point (between 6 to 12 inches) on
the measuring rod. The specific depth should be the same as the maximum designed
ponding depth (usually 6 to 12 inches).
Measurement of the Infiltration Rate
After the flow rate has stabilized for 1 hour, turn off the water and record the rate of
infiltration (the drop rate of the standing water) in inches per hour from the measuring rod
data, until the pit is empty. Use 15-minute increments if feasible.
Calculate the Design Infiltration Rate
Calculate and record the infiltration rate in inches per hour. Use the lowest hourly rate
determined in row 32 above.
To compute the design infiltration rate (Ksatd,,,g„), adjust the final measured infiltration
rates by the appropriate correction factors outlined above.
Groundwater Mounding
Over -excavate the pit to see if the test water is mounded on shallow restrictive layers or if it
has continued to flow deep into the subsurface. The soils professional should judge whether
a mounding analysis is necessary.
Falling Head Percolation Test Procedure
(as Modified for the City of Edmonds; for performance verification only)
Space tests uniformly throughout the area. If soil conditions are highly variable, more tests
may be required.
Preparation of Test Hole
The diameter of each test hole is 8 inches.
The depth of each test is to the proposed depths of the absorption systems or to the most
limiting soil horizon.
To expose a natural soil surface, scratch the bottom of the hole with a sharp pointed
instrument and remove the loose material from the test hole.
Set a PVC pipe (6 inch -inner -diameter, 4 foot long) into the hole and press into the soil
6 inches.
Place 2 inches of 0.5- to 0.75-inch rock in the pipe to protect the bottom from scouring
when water is added.
Soaking Period
In sandy soils with little or no clay, soaking is not necessary (proceed to Measurement of
the Percolation Rate).
Carefully fill the pipe with at least 12 inches of clear water. Maintain the depth of water for
at least 4 hours (and preferably overnight if clay soils are present).
If, after filling the pipe twice with 12 inches of water, the water seeps completely away in
less than 10 minutes, the test can proceed immediately (proceed to Measurement of the
Percolation Rate).
ADDENDUM CHECKLIST
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Within each blank cell, enter comment codes as follows:
C = Complete R = Revise (i.e., make corrections)
N/A = Not Applicable M = Missing (i.e., please include)
IC = Incomplete
Measurement of the Percolation Rate
Except for sandy soils, make percolation rate measurements 15 hours but no more than
30 hours after the soaking period began.
Adjust the water level to 6 inches above the gravel (or 8 inches above the bottom of the
hole). At no time during the test is the water level allowed to rise more than 6 inches above
the gravel.
Immediately after adjustment, measure the water level from a fixed reference point to the
nearest 1/16th inch at 30-minute intervals. Continue the test until two successive water level
drops do not vary by more than 1/16 inch within a 90-minute period. At least three
measurements are to be made.
After each measurement, readjust the water level to the 6-inch level.
Use the last water level drop to calculate the percolation rate.
In sandy soils or soils in which the first 6 inches of water added after the soaking period
seeps away in less than 30 minutes, make water level measurements at 10-minute intervals
for a 1-hour period. Use the last water level drop to calculate the percolation rate.
Calculate the Design Infiltration Rate
Calculate the percolation rate for each test site by dividing the time interval used between
measurements by the magnitude of the last water level drop. This calculation results in a
percolation rate in minutes/inch. To determine the percolation rate for the area, average the
rates obtained from each hole. (If tests in the area vary by more than 20 minutes/inch,
variations in soil type are indicated. Under these circumstances, percolation rates should not
be averaged.)
To compute the design infiltration rate (Ksatdesign), adjust the final percolation rates by the
appropriate correction factors outlined above.
Method 3 — Soil Grain Analysis
(SWMMWW Volume III, Section 3.3.6)
For infiltration basins and trenches, perform the grain size analysis for each defined layer
below the infiltration facility to a depth below the facility bottom of 2.5 times the maximum
depth of water in the pond, but not less than 10 feet.
For large infiltration facilities serving drainage areas of 10 acres or more, soil grain size
analyses are performed on layers up to 50 feet deep (or no more than 10 feet below the
water table).
For bioretention areas, each defined layer is analyzed below the top of the final bioretention
area subgrade to a depth of at least 3 times the maximum ponding depth, but not less than
3 feet (1 meter).
For permeable pavement, each defined layer is analyzed below the top of the final subgrade
to a depth of at least 3 times the maximum ponding depth within the base (reservoir) course,
but not less than 3 feet (1 meter).
If the licensed professional conducting the investigation determines that deeper layers will
influence the rate of infiltration for the facility, soil layers at greater depths may be
considered when assessing the site's hydraulic conductivity characteristics.
►_1DID] 40U111L[y.IXy34&IMI
Within each blank cell, enter comment codes as follows:
C = Complete R = Revise (i.e., make corrections)
N/A = Not Applicable M = Missing (i.e., please include)
IC = Incomplete
Use the following relationship to determine the initial hydraulic conductivity:
loglo (Ksar) _ -1.57 + 1.90DIo + 0.015D60 - 0.013D90 - 2.08ff..O,
Where, D,o, D60, and D90 are the grain sizes in min for which 10 perccnt, 60 percent, and
90 percent of the sample is more fine and ffnes is the fraction of the soil (by weight) that
passes the US 4200 sieve (Ksat is in cm/s).
Compaction effects must be taken into account when estimating hydraulic conductivity
where applicable.
Reviewer:
Review Date:
Reviewer Phone #:
Reviewer Comments:
ADDENDUM CHECKLIST